A variety of imaging modalities have been applied to generating images of the retina or fundus of the eye. Two well established techniques are widefield imaging typically accomplished by classic fundus cameras and confocal scanning laser ophthalmoscope (cSLO) imaging designs. Fundus cameras illuminate large fields of the retina typically with a flash lamp and take still photos with a two-dimensional camera. To avoid detecting specular reflections of the illumination light at the cornea, a ring-shaped mirror reflects the illumination light to the eye creating an annular aperture near the cornea, which does not overlap with the central disc like aperture which is used for detection. Thus a separation of the illumination and detection path near the cornea is realized, which is known as aperture or pupil splitting. To prevent specular reflections of the illumination light at optical surfaces of the fundus camera itself, especially from the ophthalmic lens, from being detected by the camera, so called dark spots in the illumination path prevent that specific surface area of the optics from being illuminated. Fundus cameras have the advantage that taking images of the retina is fast, thus for example no movement artifacts are observed, and they realize a high lateral resolution with high signal level and dynamic range.
Widefield imaging systems such as fundus cameras have the following limitations:                1. They collect light from all depths within the eye, leading to issues with contrast and reflexes. Thus the contrast in fundus images can be low, which is especially observed in eyes having cataracts.        2. The need to eliminate reflexes puts strict constraints on the system, limiting the field of view to roughly 60 degrees, and making it difficult to combine with other modalities.        3. Finally, the full field of view of the imaging system is used simultaneously, eliminating the option of dynamic adaptive optics for image enhancement.        
Another concept of imaging the retina is realized by point confocal scanning systems. These systems image the fundus by illuminating a small spot of the retina with a laser and detecting the reflected or emitted light (e.g. in case for fluorescence modes) by a detector with a pinhole in front of the detector. This pinhole is optically conjugated to the illuminated spot on the retina. Due to the confocal arrangement of illumination and detection, stray-light and out of focus light is suppressed. For imaging the retina the spot is laterally scanned. Confocal scanners have the advantage of suppressing out of focus light, thus showing high contrast images.
Point scanning confocal imaging systems such as a cSLO have the following limitations:                1. They operate with point illumination, requiring the use of lasers or SLDs, which are expensive, and creating a high instantaneous intensity on the eye, making safety more challenging.        2. As each point is imaged sequentially, they require fast transverse scanning to avoid motion artifacts, which is expensive, and may require resonant scanners, which limit imaging flexibility.        3. It can be difficult to achieve enough confocality to completely eliminate the eye reflex, and such a confocal system causes structures such as the optic disk to appear dark because they are not in the plane of the retina.        
Another concept for imaging the retina is realized in line scanning systems. In contrast to point confocal systems a line instead of a point is illuminated by a laser and detected at a camera. These systems maintain confocal suppression of out of focus light perpendicular to the line but lack the confocal suppression along the line. The line width in detection can be adapted to the amount of suppression of out of focus light that is necessary. Line scanning has been combined with aperture splitting known from classical fundus imaging (see for example Muller et al. US Patent Publication No. 2010/0128221) and also with ellipsiodal modifications of the illumination pupil to avoid vignetting and to get a uniformly illuminated line at the retina. Muller et al. also discloses so called non-de-scanned or imaged systems, where the scanning over the retina is realized only in illuminating or scanning line illumination over the retina and scanning line detection over the retina is realized by different mechanisms.
The advantage of the line scanning system according to Muller is that it can scan faster across the retina, thus being less sensitive to motion artifacts, but at the expense of less out of focus suppression. But still motion artifacts are observed and lateral resolution and dynamic range is limited compared to fundus cameras. In addition often contrast is also limited because stray-light even coming from areas perpendicular to the line is still present in the detected signal.
Line scanning also creates new problems:                1. Variations in line intensity or linear array sensitivity lead to streaking in the image.        2. Confocality is reduced, requiring a mask to eliminate the eye reflex. This mask compromises the optical efficiency of the system, leading to dim images.        
Another concept of imaging the retina is the broad line scanner and method described in WO2012059236 by Bublitz. Bublitz discloses basic elements of a broad line fundus imager (BLFI) and methods. Bublitz further discloses the usage of LED sources with higher etendues than lasers, which is possible in contrast to a classical line scanner because the field of a broad line illumination is significantly wider than the line of a confocal line scanner. Bublitz further discloses that camera locations whose corresponding locations on the retina are not illuminated can be detected to evaluate background or stray light levels coming from out of focus region of the eye. This background is then subtracted from the image of the illuminated broad line. Bublitz also discloses a different pupil splitting for illumination and detection near the cornea than is typical for fundus cameras: instead of illumination of an annular ring, a slit is illuminated, and the detection is done via two caps of a disc at the periphery of the aperture. In addition, the orientation of the illumination slit is perpendicular to the illumination line at the retina.
Bublitz discloses a non-de-scanned detection setup using an electronic or rolling shutter camera with activated camera lines, when the corresponding line of the fundus is illuminated by the broad line or when background level is measured, but as described by German Patent Application No. DE 10 2011 053 880.1 also a de-scanned detection scheme allowing for continuous scanning can be used.
The advantage of the designs disclosed by Bublitz is that for each of the line images the benefits of classical fundus cameras are achieved: long integration times due to broad line illumination, high dynamic range, high lateral resolution due to broad line image being 2D-sampled by a high resolution 2D-camera, usage of classical light sources or LEDs having a broader wavelength spectra than lasers. Also due to faster scans, motion artifacts are reduced. In addition, a significant reduction in sensitivity to stray light by not illuminating the whole retina and measurement of background/stray light level and subtraction can be achieved. Thus the images show better contrast. But experiments have shown that further improvements are necessary to get result comparable to confocal scanners. In addition, motion artifacts still occur, due to each line of the camera having its unique illumination time window, when the data for that specific camera line is detected.